Vehicle suspension

ABSTRACT

A suspension for traction belt driven vehicles in which each arm of the suspension is permitted to deflect independently of the remaining arms. Movement of the suspension arms about a common pivot shaft is resisted by elastomeric torsion springs attached to the ends of the suspension arms surrounding spaced axial portions of the pivot shaft such that the arms extend in cantilevered arrangement from the shaft. Idler pulleys are rotatably attached to the free end of each arm for contacting the running traction belt.

United States Patent Kramer [4 1 Dec. l9, 1972 [54] VEHICLE SUSPENSION[72] Inventor:

[73] Assignee: The B. F. Goodrich Company, New

York, NY.

[22] Filed: May 15, 1970 [21] App1.No.: 37,512

James H. Kramer, Akron, Ohio [52] US. Cl. ..305/27, 180/5, 267/57.1,280/124 A [51] Int. Cl. ..B62d 55/16 [58] Field of Search.....305/27;267/57.1, 57.1 A, 63; 280/124 A, 124 R; 180/5 R [56] References CitedUNITED STATES PATENTS 2,773,699 12/1956 Grumman ..267/57.1 R X 3,336,0218/1967 Kramer ..267/l54 2,444,759 7/1948 Swennes ..305/27 2,149,2973/1939 Knox ..267/57.l A

2,162,198 6/1939 Herrington ..305/27 X 3,386,778 6/1968 Rymes 2,051,8648/1936 Knox 2,590,711 3/1952 Krotz.....

2,088,341 7/1937 Rabe ..267/57.1 A

Primary ExaminerRichard J. Johnson Attorney-W. A. Shira, Jr., Harold S.Meyer and Roger A. Johnston [57] ABSTRACT A suspension for traction beltdriven vehicles in which each arm of the suspension is permitted todeflect independently of the remaining arms. Movement of the suspensionarms about a common pivot shaft is resisted by elastomeric torsionsprings attached to the ends of the suspension arms surrounding spacedaxial portions of the pivot shaft such that the arms extend incantilevered arrangement from the shaft. Idler pulleys are rotatablyattached to the free end of each arm for contacting the running tractionbelt.

2 Claims, 4 Drawing Figures PATENTED DEC 19 m2 SHEEI 1 or INVENTOR.JAMES H.KRAMER ATTY.

PKTENTEDHEBWBYZ 3.7063181 SHEET 2 OF 2 INVENTOR. JAMES H.KRAMER TTY.

VEHICLE SUSPENSION BACKGROUND OF THE INVENTION Vehicles of the typepropelled by endless traction belts are often employed for use intraversing soft terrain such as mud, snow and sand. One popular vehicleof this type is a recreational vehicle used for traveling over snow andice and commonly known as a snowmobile. Snowmobiles are usuallypropelled by cord-reinforced elastomeric traction belts sprocket drivenand running over idler pulleys.

The suspension system most commonly used for this type of vehicle has aplurality of idlers spaced intermediate the driving sprocket and theidler sprocket at the ends of the traction belt. The suspension usuallycomprises pairs of arms extending in spaced parallel cantileveredarrangement from a common pivot shaft. The pairs of arms are urgedtoward each other arcuately about the shaft by a metal torsion springinterconnecting the pairs of arms. The weight of the vehicle is thussupported by deflection of the ends of the suspension arms whichdeflection is resisted by the torsion spring. Idler pulleys forcontacting the interior of the running traction belt are provided on theends of each of the suspension arms.

The torsion spring suspension arms and the pivot shaft are usually madeof a durable metal in order to withstand the forces encountered fromimpact of the traction belt withobstacles such as rocks or irregularfrozen surfaces. Furthermore, the torsion springs must not only providesufficient force to support the static weight of the vehicle, but mustbe designed to sustain high frequency deflection while being subjectedto contact with water, snow and ice. During service operation of thesnowmobile, the prolonged exposure to snow and ice often causescorrosion of metal torsion springs and the moving surfaces of theinterconnecting suspension elements and thus early failure of thesuspension, or, in some cases, seizure of the suspension arms renderingthe arms no longer deflectable. In view of these service problemsencountered by the suspension during normal operation of the vehicle, ithas been desired to provide a suspension for the vehicle which is notaffected adversely by the operating environment and yet one that can befabricated from materials other than costly corrosion resistant orstainless metals.

Furthermore, it has long been desirable to provide a suspension for thesnowmobile which permits independent deflection of one side of thetraction belt without causing deflection of the suspension on theopposite side of the belt. Heretofore, in the suspensions for thesnowmobile, the suspension arms, as mentioned above, have been attachedto the pivot shaft in pairs such that relative rotation of one arm ineach pair with respect to the other arm of that pair, is not permitted.Metal torsion springs have been most commonly used to interconnect thepairs of arms in the manner resiliently resisting relative rotationbetween pairs of arms. The pairs of arms are disposed about the pivotshaft with one pair extending in a direction leading the pivot shaft andthe other pair of arms trailing the pivot shaft such that deflection ofthe suspension causes scissoring of the pairs of arms with respect toeach other. Thus, if the traction belt encounters an object on only oneside of the belt causing deflection of one forward suspension arm, thecorresponding opposite suspension arm on the opposite side of the beltis also caused to deflect and similarly for deflection of either one ofthe pair of trailing arms. This renders the suspension, and hence, thetraction belt, generally noncompliant with surfaces which cause thetraction belt to be inclined transversely with respect to the vehicle.This tends to reduce traction, damage the belt, render the vehicle roughriding and incapable of traversing satisfactorily uneven terrain, andoften results in loss of control of the vehicle.

SUMMARY OF THE INVENTION The present invention provides a solution tothe above-described problem of providing a satisfactory suspension forvehicles of the type utilizing elastomeric traction belts for traversingsoft terrain and particularly for the type of vehicle known as thesnowmobile. The essence of the improved suspension is the provision ofelastomeric spring means supporting the arms of the suspension forindividual pivotal movement about a common axis with the spring meansresiliently resisting that movement.

The suspension of the present invention, in its preferred embodiment,employs a rigid shaft or bar mounted transversely of the vehicle with aplurality of elastomeric torsion springs surrounding and contactingportions of the bar in axially spaced arrangement along the bar.Suspension arms are attached to the bar with respectively one armengaging each of the elastomeric torsion springs with each arm extendingin cantilevered arrangement from the bar. The arms are arranged in tworows, one row extending forward of the rigid bar and with the second rowof arms trailing the bar such that the included angle between the rowsis an obtuse angle. Rotational movement of each arm about the bar isindividually resisted by the associated elastomeric torsion springs.Idler pulleys are provided respectively on the ends of each of thesuspension arms for contacting the interior surface of the runningtraction belt thus providing a vehicle suspension.

The present invention thus provides a solution to the problem ofproviding an independent suspension for a snowmobile.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a portion ofa vehicle suspension, having a pair of leading arms and a pair oftrailing arms, incorporating the presently preferred embodiment of theinvention;

FIG. 2 is a side elevation view of the embodiment of FIG. 1;

FIG. 3 is a cross section take along section indicating lines 33 of FIG.1 showing the details of the elastomeric spring between the arm and thepivot shaft; and,

FIG. 4 is a view similar to FIG. 3 illustrating an alternative form ofthe embodiment of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIGS. 1, 2 and 3,the suspension has a pivot shaft or bar 10 of rigid material, preferablymetal, with a preferably transverse polygonal cross section that isadapted to be supported on a vehicle by spaced mounting brackets 11,each having one end rigidly attached to an end of the pivot shaft andthe other end formed with a bolt hole or other expedient adapted formounting on a vehicle frame, not shown. A pair of leading suspensionarms 12 is provided, with each am having a hollow hub portion 13 withthe pivot shaft 10 passing through the bore of the hub. The arms 12 arearranged adjacent the ends of the bar 10 extending cantileveredtherefrom in axially spaced parallel arrangement. A pair of trailingarms 14 having hollow hubs 15, with the pivot shaft 10 passingtherethrough, are disposed in axially spaced cantilevered arrangementaxially intermediate the pair of arms 12. The pair of arms 14 extendgenerally from the opposite side of the bar from the arms 12 in a mannersuch that an obtuse central angle is subtended between the pairs of arms12 and 14. Each of the pairs of arms 12, 14 has an elastomeric torsionspring provided in the bore of the hubs 13,15 intermediate the hubs andthe shaft 10. If desired, spacers (not illustrative) may be provided onthe pivot shaft to retain the arms'in their respective axial positions.

The weight of the vehicle is supported by torsional preload on each ofthe elastomeric springs and running deflection of the traction belt isabsorbed by rotation of the suspension arms respectively about the rigidshaft and with consequent deflection of the torsion springs. Rotation ofone of the suspension arms about the shaft is resiliently resisted byonly one of the elastomeric springs and, hence, no rotational force isexerted on any of the other suspension arms. Each of the arms is thusindependently supported from the rigid shaft in a manner which does notaffect the other arms. Furthermore, the present invention has nometal-to-metal contacting surfaces in the pivot portions and thereforeis not subject to failure or seizure by corrosion.

Each of the torsion springs S, as illustrated in FIG. 3, has an annularring of of elastomer with an inner shell 21 of metal bonded thereto, theshell having a polygonal bore engaging the bar 10 of like crosssectional configuration and dimensions in a manner preventing relativerotation therebetween. Each elastomeric ring 20 further has an outershell 22 surrounding the outer periphery thereof, preferably in the formof two half shells, with each half shell bonded to the elastomer, hadhaving a radial lug portion 23 extending from its outer periphery andengaging a corresponding recess in the hub, such as 15, of the arm inwhich it is positioned. This feature permits longitudinal assembly ofthe spring into the hub of the arm in a manner preventing relativerotation between the arm and the shell 22 of the spring. Theconstruction of the elastomeric spring in the presently preferred formof the invention is that disclosed in US. Pat. No. 3,336,021. However,the invention may also be practiced with elastomeric torsion springsother than the particular spn'ng form disclosed in the referencedpatent.

Each of the pairs of suspension arms 12,14 has a spindle hub 16 providedon the free end thereof with an idler wheel 17 attached to the spindlehub by suitable means, such as a bolt 18, the outer end of which isthreaded and provided with a nut 19, so that the wheels 17 are free torotate about the bolt. In the preferred practice of the invention,sleeve bearings and thrust H washers (not illustrated) are provided onthe bolts 18 to permit free rotation of the idler wheels 17.

Referring now to FIG. 4, an alternative form S of the embodiment of FIG.1 is shown in which a typical one of the suspension arms, designated 30,is shown as having a hollow hub portion 31. A rigid pivot shaft 32 isreceived through the bore of hub 31 with the shaft 32 having a circularcross section a portion of the outer periphery of which islongitudinally splined in the region axially coincident with the hub 31of the suspension arm. An elastomeric ring 33, of generally annularshape, is provided radially intermediate the shaft 32 and the hub 31 ofthe arm. .The ring 33 preferably has an outer shell 34 enclosing theouter periphery of the ring 33 and bonded theretopreventing relativerotation between the outer periphery of the spring and the innerperiphery of the shell. The shell 34 is preferably formed of two similarcircumferential half-shells with lug portions 35 engaging recesses foundin the hub 31 of the arm, similar to the embodiment of FIG. 1 and FIG.3. The ring 33 further has an inner shell 36, provided intermediate theelastomeric material and the shaft 32, with the inner shell 36 havingthe external surface bonded to the elastomeric material and the innerperiphery splined axially to engage the corresponding axial splinesprovided on the outer periphery of the shaft 32. The embodiment of FIG.4 is employed where it is desired to provide greater torsional preloadson the elastomeric spring and thus utilizes the spline for ab-- sorbingand transmitting the greater preload torque.

The present invention thus comprises a suspension for track drivenvehicles having a plurality of suspension arms independently andresiliently connected to a common rigid pivot shaft by means ofindividual axially spaced elastomeric torsion springs with thesuspension arms extending in cantilevered arrangement from the pivotshaft and with each arm adapted to be deflected rotationally about thepivot shaft independently of the remaining suspension arms.

Modifications and adaptations of the invention may be made by thosehaving ordinary skill in the art and the invention is limited only bythe spirit and scope of the following claims.

I claim:

l. A suspension for track propelled vehicles comprising:

a. rigid pivot means including a rigid bar having a polygonal transversecross section and a pair of support brackets each having an end portionrigidly attached respectively one to each end of said bar with mountingportions formed on the free end of each bracket for attachment to theframe of a vehicle to be suspended;

. a plurality of torsion springs formed of elastomeric material eachcircumferentially engaging individual axially spaced portions of the barof said pivot means in a manner independently and resiliently resistingrotation of each of said springs about said pivot means;

c. a plurality of rigid arms each having an end portion surrounding andengaging one of said springs in a manner resiliently resisting rotationof each arm about said pivot means, respectively, with each of said armsextending in cantilevered arrangement from said pivot means with atleast two of said arms disposed in diverging relationship with respectto each other about said pivot means; and,

an idler member attached to each of said arm members and adapted tooperatively contact guide portions of an endless track.

The suspension defined in claim 1, wherein each torsion springcomprises:

a metallic inner shell having a polygonally shaped axially extendingcentral opening and a cylindrical outer surface,

an annular metallic outer shell coaxial with said inner shell andradially spaced therefrom,

an annulus of elastomeric material between said inner and outer shellintegrally bonded to both,

1. A suspension for track propelled vehicles comprising: a. rigid pivotmeans including a rigid bar having a polygonal transverse cross sectionand a pair of support brackets each having an end portion rigidlyattached respectively one to each end of said bar with mounting portionsformed on the free end of each bracket for attachment to the frame of avehicle to be suspended; b. a plurality of torsion springs formed ofelastomeric material each circumferentially engaging individual axiallyspaced portions of the bar of said pivot means in a manner independentlyand resiliently resisting rotation of each of said springs about saidpivot means; c. a plurality of rigid arms each having an end portionsurrounding and engaging one of said springs in a manner resilientlyresisting rotation of each arm about said pivot means, respectively,with each of said arms extending in cantilevered arrangement from saidpivot means with at least two of said arms disposed in divergingrelationship with respect to each other about said pivot means; and, d.an idler member attached to each of said arm members and adapted tooperatively contact guide portions of an endless track.
 2. Thesuspension defined in claim 1, wherein each torsion spring comprises: a.a metallic inner shell having a polygonally shaped axially extendingcentral opening and a cylindrical outer surface, b. an annular metallicouter shell coaxial with said inner shell and radially spaced therefrom,c. an annulus of elastomeric material between said inner and outer shellintegrally bonded to both, d. the said pivot means having the saidaxially spaced portions formed with a cross section of polygonal shapecomplementary to and axially interfitting with the central opening ofeach of said inner shells, and e. the outer surface of said outer shelland the inner surface of the portion of each of said arms surroundingsaid pivot means having cooperating complementarily shaped portions forpreventing relative rotation.